The present invention relates to an apparatus, system, and method for testing and exercising the pelvic floor musculature.
The pelvic floor muscles are a mind-controlled and layered muscle group which surrounds the urethra, vagina, and rectum, and which, together with the sphincter muscles, functions to control these openings. This musculature also serves to support the urethra, bladder, and uterus, as well as to resist any increases in the abdominal pressure developed during physical exertion. The muscle group includes both longitudinal muscles and annular muscles.
Training of the pelvic floor musculature has proven efficient in preventing and treating several conditions, e.g. incontinence. Numerous exercises exist for training the pelvic floor musculature. For a number of reasons, the effect of these exercises varies among people. Also, it is known that mechanical vibrations in a range below approx. 120 Hz applied to the tissue increase the training effect of such exercises. As the musculature becomes stronger, it will be possible to measure the training effect by measuring the ability of the musculature to retract.
Measuring Principle and Measurement Parameters
A stronger muscle can be expected to dampen an amplitude of oscillation applied thereto more than a weaker muscle. A first principle of measurement, therefore, may be to measure the amplitude dampening of an imposed oscillation. The measured amplitude can be described as A˜A0 sin(ωt). A relative amplitude dampening is defined as:ΔA=(A−A0)/A0  (1)whereA is the amplitude measured,A0 is the amplitude imposed,ω is the angular frequency of the oscillation imposed, andt is time.
It is considered well known to a person skilled in the art that the output signal from an accelerometer may represent an acceleration which can be integrated to obtain a velocity and a second time to obtain a displacement or deflection. It is also well known that accelerations, velocities, and displacements of equal magnitudes and opposite directions have average values of zero, and that meaningful parameters hence must be based on absolute values such as maximum acceleration, velocity, or amplitude, for example. In view of the above, it is clear that the dimensionless attenuation ΔA can be calculated from displacements in mm, velocities in m/s, accelerations in m/s2, and/or electrical signals input to the oscillator and output from the accelerometer. In any case, the attenuation ΔA can be expressed in dB, calibrated to display the force in Newton (N), etc. according to need and in manners known for persons skilled in the art.
During exercise, the volume of the muscle cells increases and the skeleton of the cells becomes more rigid. In another model, therefore, the pelvic floor musculature can be regarded as a visco-elastic material, i.e. as a material having properties between a fully elastic material and an entirely rigid and inelastic (viscous) material. For example, a slack or weak muscle can be expected to exhibit relatively “elastic” properties, whereas a tight or strong muscle can be expected produce more resistance and thus relatively “viscous” properties. Formally:                stress is the force acting to resist an imposed change divided by the area over which the force acts. Hence, stress is a pressure, and is measured in Pascal (Pa), and        strain is the ratio between the change caused by the stress and the relaxed configuration of the object. Thus, strain is a dimensionless quantity.        
The modulus of elasticity is defined as the ratio λ=stress/strain. The dynamic modulus is the same ratio when the stress arises from an imposed oscillation. When an oscillation is imposed in a purely elastic material, the elongation measured is in phase with the imposed oscillation, i.e. strain occurs simultaneously with the imposed oscillation. When the oscillation is imposed in a purely viscous material, the strain lags the stress by 90° (π/2 radians). Visco-elastic materials behave as a combination of a purely elastic and a purely viscous material. Hence, the strain lags the imposed oscillation by a phase difference between 0 and π/2. The above can be expressed through the following equations:σ=a0 sin(ωt)  (2)ϵ=a0 sin(ωt−φ)  (3)λ=σ/ϵ  (4)where                σ is stress from an imposed oscillation (Pa)        ϵ is strain (dimensionless)        ω is the oscillator frequency (Hz)        t is time (s),        φ is the phase difference varying between 0 (purely elastic) and π/2 (purely viscous), and        λ is the dynamic module.        
Biomechanically, this may be interpreted as that a stronger muscle increases the force resisting the oscillation and thereby “delays” the vibrations measured by the accelerometer. This is equivalent with that a strong muscle is stiffer or “more viscous” than a slack, gelatinous, and “more elastic” muscle.
A general problem in the prior art in the field is that measurement values are often given in terms of pressure, e.g. in millimeter water column. As pressure is a force divided by an area, the pressure reported will depend on the area of the measuring apparatus, and hence on the supplier. Therefore, in the literature in the field, measurement values are often given in the format ‘<Supplier_name> mmH2O’, for example. In turn, this results in that measurement values from different apparatuses are not directly comparable, and consequently a need exists for supplier independent measurement values in the field of the invention.
U.S. Pat. No. 6,059,740 discloses an apparatus for testing and exercising pelvic floor musculature. The apparatus includes an elongate housing adapted for insertion into the pelvic floor aperture. The housing is divided longitudinally into two halves, and includes an oscillator as well as a cut out and equipment for measuring pressure applied to the housing halves from the pelvic floor musculature. The apparatus indicates the force pressing together the two halves in Newton (N), and essentially measures the training effect on muscles acting radially on the housing.
A need exists for an apparatus which also measures and trains the musculature running in parallel with a longitudinal direction of the apparatus or pelvic floor opening.
The object of the present invention is to address one or more of the above problems, while maintaining the advantages of prior art.